Received-SPF: pass (google.com: domain of linux-kernel+bounces-99283-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Sender: Guenter Roeck <groeck7@gmail.com>
Date: Mon, 11 Mar 2024 10:04:38 -0700
From: Guenter Roeck <linux@roeck-us.net>
To: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org,
	regressions@lists.linux.dev
Subject: Re: Problems with csum_partial with misaligned buffers on sh4
 platform
Message-ID: <351dfebd-c09f-470e-8b03-cc904753b136@roeck-us.net>
References: <65ed7c95-712c-410b-84f3-58496b0c9649@roeck-us.net>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <65ed7c95-712c-410b-84f3-58496b0c9649@roeck-us.net>

On Sat, Feb 10, 2024 at 07:12:39AM -0800, Guenter Roeck wrote:
> Hi,
> 
> when running checksum unit tests on sh4 qemu emulations, I get the following
> errors.
> 

Adding to regression tracker.

#regzbot ^introduced cadc4e1a2b4d2
#regzbot title Problems with csum_partial with misaligned buffers on sh4 platform
#regzbot ignore-activity

>     KTAP version 1
>     # Subtest: checksum
>     # module: checksum_kunit
>     1..5
>     # test_csum_fixed_random_inputs: ASSERTION FAILED at lib/checksum_kunit.c:500
>     Expected ( u64)result == ( u64)expec, but
>         ( u64)result == 53378 (0xd082)
>         ( u64)expec == 33488 (0x82d0)
>     not ok 1 test_csum_fixed_random_inputs
>     # test_csum_all_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:525
>     Expected ( u64)result == ( u64)expec, but
>         ( u64)result == 65281 (0xff01)
>         ( u64)expec == 65280 (0xff00)
>     not ok 2 test_csum_all_carry_inputs
>     # test_csum_no_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:573
>     Expected ( u64)result == ( u64)expec, but
>         ( u64)result == 65535 (0xffff)
>         ( u64)expec == 65534 (0xfffe)
>     not ok 3 test_csum_no_carry_inputs
>     ok 4 test_ip_fast_csum
>     ok 5 test_csum_ipv6_magic
> # checksum: pass:2 fail:3 skip:0 total:5
> 
> The above is with from a little endian system. On a big endian system,
> the test result is as follows.
> 
>     KTAP version 1
>     # Subtest: checksum
>     # module: checksum_kunit
>     1..5
>     # test_csum_fixed_random_inputs: ASSERTION FAILED at lib/checksum_kunit.c:500
>     Expected ( u64)result == ( u64)expec, but
>         ( u64)result == 33488 (0x82d0)
>         ( u64)expec == 53378 (0xd082)
>     not ok 1 test_csum_fixed_random_inputs
>     # test_csum_all_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:525
>     Expected ( u64)result == ( u64)expec, but
>         ( u64)result == 65281 (0xff01)
>         ( u64)expec == 255 (0xff)
>     not ok 2 test_csum_all_carry_inputs
>     # test_csum_no_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:565
>     Expected ( u64)result == ( u64)expec, but
>         ( u64)result == 1020 (0x3fc)
>         ( u64)expec == 0 (0x0)
>     not ok 3 test_csum_no_carry_inputs
>     # test_ip_fast_csum: ASSERTION FAILED at lib/checksum_kunit.c:589
>     Expected ( u64)expected == ( u64)csum_result, but
>         ( u64)expected == 55939 (0xda83)
>         ( u64)csum_result == 33754 (0x83da)
>     not ok 4 test_ip_fast_csum
>     # test_csum_ipv6_magic: ASSERTION FAILED at lib/checksum_kunit.c:617
>     Expected ( u64)expected_csum_ipv6_magic[i] == ( u64)csum_ipv6_magic(saddr, daddr, len, proto, csum), but
>         ( u64)expected_csum_ipv6_magic[i] == 6356 (0x18d4)
>         ( u64)csum_ipv6_magic(saddr, daddr, len, proto, csum) == 43586 (0xaa42)
>     not ok 5 test_csum_ipv6_magic
> # checksum: pass:0 fail:5 skip:0 total:5
> 
> Note that test_ip_fast_csum and test_csum_ipv6_magic fail on all big endian
> systems due to a bug in the test code, unrelated to this problem.
> 
> Analysis shows that the errors are seen only if the buffer is misaligned.
> Looking into arch/sh/lib/checksum.S, I found commit cadc4e1a2b4d2 ("sh:
> Handle calling csum_partial with misaligned data") which seemed to be
> related. Reverting that commit fixes the problem.
> This suggests that something may be wrong with that commit. Alternatively,
> of course, it may be possible that something is wrong with the qemu
> emulation, but that seems unlikely.
> 
> Thanks,
> Guenter